U.S. patent application number 15/564372 was filed with the patent office on 2018-05-10 for lighting device for a motor vehicle headlamp.
The applicant listed for this patent is ZKW Group GmbH. Invention is credited to Josef PLANK, Lukas TAUDT.
Application Number | 20180128443 15/564372 |
Document ID | / |
Family ID | 56681897 |
Filed Date | 2018-05-10 |
United States Patent
Application |
20180128443 |
Kind Code |
A1 |
TAUDT; Lukas ; et
al. |
May 10, 2018 |
LIGHTING DEVICE FOR A MOTOR VEHICLE HEADLAMP
Abstract
The invention relates to a lighting device (1) for a headlamp,
in particular a motor-vehicle headlamp, comprising a plurality of
light sources (100), a light-guiding device (10) with a plurality
of light-guiding elements (11, 12, 13), and a downstream imaging
optical element (200), wherein each light-guiding element (11, 12,
13) has a light infeed face and a light exit face, wherein the
light-guiding elements (11, 12, 13) are arranged in at least one
row, wherein the light-guiding elements of at least one row are
configured as main beam light-guiding elements (11) and form a main
beam row, wherein each main beam light-guiding element (11)
comprises a lower light-guiding face (24), wherein the lower
light-guiding face (24) has, at least in the region in which the
light beams (52) are reflected, structures (25) at least in
regions.
Inventors: |
TAUDT; Lukas; (Wieselburg,
AT) ; PLANK; Josef; (Purgstall/Erlauf, AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ZKW Group GmbH |
Wieselburg |
|
AT |
|
|
Family ID: |
56681897 |
Appl. No.: |
15/564372 |
Filed: |
July 18, 2016 |
PCT Filed: |
July 18, 2016 |
PCT NO: |
PCT/AT2016/060008 |
371 Date: |
October 4, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F21S 41/24 20180101;
F21Y 2115/10 20160801; F21S 41/663 20180101; F21S 41/285 20180101;
F21S 41/143 20180101 |
International
Class: |
F21S 41/24 20060101
F21S041/24; F21S 41/20 20060101 F21S041/20; F21S 41/141 20060101
F21S041/141 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 28, 2015 |
AT |
A 50672/2015 |
Claims
1. A lighting device (1) for a headlamp, in particular a
motor-vehicle headlamp, comprising a plurality of light sources
(100), a light-guiding device (10) with a plurality of
light-guiding elements (11, 12, 13), and a downstream imaging
optical element (200), wherein each light-guiding element (11, 12,
13) has a light infeed face and a light exit face, wherein the
light-guiding elements (11, 12, 13) are arranged in at least one
row, characterised in that the light-guiding elements of at least
one row are configured as main beam light-guiding elements (11) and
form a main beam row, wherein each main beam light-guiding element
(11) comprises a lower light-guiding face (24), wherein the lower
light-guiding face (24) has, at least in the region in which the
light beams (52) are reflected, structures (25) at least in
regions.
2. The lighting device according to claim 1, characterised in that
the structures (25) are formed in the region of the lower
light-guiding face (24) which borders the light exit face (23) and
in which the light is reflected.
3. The lighting device according to claim 1 or 2, characterised in
that the lower light-guiding face (24) totally reflects the
coupled-in light beams.
4. The lighting device according to any one of claims 1 to 3,
characterised in that the structures comprise structural elements
(25), which have a periodic geometry.
5. The lighting device according to any one of claims 1 to 4,
characterised in that the structures are rib-like, wherein the ribs
(25) are oriented transversely to an optical axis (16) of the
lighting device.
6. The lighting device according to claim 5, characterised in that
the ribs (25) have a width of 0.2 to 0.4 mm and a height of 0.15 to
0.03 mm.
7. The lighting device according to claims 2 and 6, characterised
in that, starting from the light exit face, 6 to 15 ribs (25) are
formed on the lower light-guiding face (24).
8. The lighting device according to any one of claims 1 to 7,
characterised in that the light-guiding elements (11, 12, 13) are
arranged in exactly three rows arranged one above the other, which
together form a main beam distribution.
9. The lighting device according to claim 8, characterised in that
the lowermost row (11) is the main beam row.
10. The lighting device according to any one of claims 1 to 7,
characterised in that all light-guiding elements are formed as main
beam light-guiding elements arranged in exactly one row.
11. The lighting device according to any one of claims 1 to 10,
characterised in that the light exit faces (23) of the
light-guiding elements (11, 12, 13) are part of a joint light exit
face (23'), wherein individual light exit faces (23) border one
another.
12. A motor-vehicle headlamp comprising a lighting device (1)
according to any one of claims 1 to 11.
Description
[0001] The invention relates to a lighting device for a headlamp,
in particular a motor vehicle headlamp, comprising a plurality of
light sources, a light-guiding device with a plurality of
light-guiding elements, and a downstream imaging optical element,
wherein each light-guiding element has a light input face and a
light exit face, wherein the light-guiding elements are arranged in
at least one row.
[0002] Lighting units of this type, which are also referred to as
pixel light modules, are customary in vehicle construction and by
way of example serve for the imaging of glare-free main beam, in
that the light is generally radiated from a plurality of artificial
light sources and is bundled by a corresponding plurality of
adjacently arranged light guides (optical attachment/primary
optics) in the radiation direction. The light guides have a
relatively small cross-section and therefore emit the light of the
individual light sources assigned to them in a very concentrated
manner in the radiation direction. Pixel light headlamps are very
flexible in respect of the light distribution, since the
illumination intensity can be individually controlled for each
pixel, i.e. for each light guide, and any desired light
distributions can be realised.
[0003] On the one hand, the concentrated radiation of the light
guides is desired, for example in order to comply with legal
requirements relating to the light-dark line of a motor vehicle
headlamp or in order to provide adaptive flexible masking
scenarios, and on the other hand disruptive inhomogeneities form in
regions of the light pattern in which a uniform, concentrated and
directed lighting is desired, for example in the case of the main
beam distribution.
[0004] This problem could be improved by reducing the height of the
main beam distribution, however this is contrary to customer
requirements. There is thus a need for improved measures for
homogenising the main beam distribution.
[0005] Various measures and methods are known from the prior art
which on the one hand are based on defocusing and on the other hand
on light scattering, for example by means of light-scattering
structures.
[0006] Document U.S. Pat. No. 8,011,803 B2 relates to a fog
headlamp which comprises collimating optical attachments with
attached corrugated deflection face, which is inclined relative to
the primary radiation direction of the LED. On the one hand, the
light is thus deflected, but also scattered, so that the
homogeneity is improved.
[0007] Document DE 2009 053 581 B3 relates to the primary optics of
a matrix/pixel module. The end exit face of the optics is provided
with a corrugated pad structure.
[0008] Document DE 10 2008 005 488 A1 discloses a fine-structured
face for the optical unit with a plurality of structural elements,
by means of which the light flecks are widened in the horizontal
direction. With superimposition of the light flecks, the edges
disappear, thus resulting in a more homogeneous overall light
distribution.
[0009] Document DE 10 2010 027 322 A1 describes refractive
micro-optical components on the light exit surface of a primary
optics.
[0010] Document EP 2 587 125 A2 discloses microstructures on the
light exit face of the primary optics of a pixel headlamp.
[0011] Document U.S. Pat. No. 5,727,108 discloses prismatic
delimiting faces for a compound parabolic concentrator (CPC)
optical attachment.
[0012] The object of the invention is to create a lighting device
for headlamps that on the one hand enables a more homogeneous main
beam distribution and on the other hand enables a concentrated and
directed lighting of a main beam region.
[0013] This object is achieved with a lighting device for headlamps
of the type mentioned in the introduction, which is characterised
in accordance with the invention in that the light-guiding elements
of at least one row are configured as main beam light-guiding
elements and form a main beam row, wherein each main beam
light-guiding element comprises a lower light-guiding face, wherein
the lower light-guiding face, at least in the area in which the
light beams are reflected, has structures at least in regions.
[0014] The invention constitutes a technically simple and
economical measure for locally influencing the light distribution
in the respective main beam light-guiding elements and therefore
for providing a more homogeneous main beam distribution.
[0015] The basic structure of light-guiding elements and optical
attachments for pixel light lighting devices for headlamps is known
per se. The light-guiding elements are produced for example from
plastic, glass, or any other materials suitable for guiding light.
The light-guiding elements are preferably produced from a silicone
material. The light-guiding elements are typically embodied as
solid bodies and preferably consist of a single continuous optical
medium, wherein the light is guided within this medium. The
light-guiding elements typically have a substantially square or
rectangular cross-section and usually widen in the light radiation
direction, in a manner known per se. In an alternative embodiment,
the light-guiding elements can be realised as open collimators.
[0016] These structures are advantageously formed in the region of
the lower light-guiding face that borders the light exit face and
in which the light is reflected. By arranging the structures only
in the vicinity of the light exit face of the respective main beam
light-guiding elements of the main beam row, in particular the
superimposition of reflected light beams and the directly radiated
light can thus be improved.
[0017] The light radiated from the light source and coupled into
the light-guiding element is expediently totally reflected by the
lower light-guiding face.
[0018] The structures formed on the lower light-guiding face
advantageously comprise structural elements that have a periodic
geometry.
[0019] It has been found that it is particularly advantageous if
the structures are formed in a rib-like manner, wherein the ribs
are oriented transversely to an optical axis of the lighting
device.
[0020] The ribs can have a width of approximately 0.1 to 0.4 mm and
a height of 0.015 to 0.03 mm.
[0021] In a variant, it is provided that, starting from the light
exit face, 6 to 15 ribs are formed in the lower light-guiding
face.
[0022] According to experience, the structure of a lighting device
for pixel light headlamps is particularly efficient if the
light-guiding elements are arranged in exactly three rows arranged
one above the other, which together form a main beam distribution.
With an arrangement of this type, the upper row can be formed as a
forefield row, the middle row can be formed as an asymmetry row,
and the lower row can be formed as a main beam row, wherein the
main beans formed of main beam light-guiding elements is provided
with structures as disclosed and described herein. The lowermost
row is expediently the main beam row.
[0023] In another embodiment, all light-guiding elements can be
formed as main beam light-guiding elements, which are arranged in
exactly one row. Lighting devices of this type are also referred to
as pixel main beam modules.
[0024] The light-guiding elements of the rows are preferably
arranged as closely to one another as possible, whereby
inhomogeneities in the light pattern can be reduced once again. In
a development of the invention, the light exit faces of the
individual light-guiding elements can therefore be part of a joint
light exit face, wherein the individual light exit faces border one
another. The joint light exit face is typically a curved face,
which usually follows the Petzval face of the imaging optics (for
example an imaging lens). For specific applications, however,
deliberate deviations can be inserted in the curvature in order to
utilise imaging errors in the edge region for light
homogenisation.
[0025] A further subject of the invention relates to a headlamp, in
particular a motor vehicle headlamp, which comprises a lighting
device according to the invention as disclosed herein. Headlamps of
this type are also referred to as pixel light headlamps.
[0026] The invention and advantages thereof will be described in
greater detail hereinafter on the basis of non-limiting examples,
which are illustrated in the accompanying drawings. The drawings
show, in:
[0027] FIG. 1 a perspective illustration of the basic structure of
a lighting device according to the invention,
[0028] FIG. 2 an illustration of the total light distribution
obtained with the lighting device from FIG. 1,
[0029] FIG. 3 a detailed view of an optical attachment from FIG. 1
in the light propagation direction,
[0030] FIG. 4 a side view of a main beam light-guiding element
according to the prior art,
[0031] FIG. 5 a light intensity distribution (light intensity
simulation) of a main beam light-guiding element from FIG. 4,
[0032] FIG. 6 an intensity profile curve of the light intensity
distribution from FIG. 5,
[0033] FIG. 7 a side view of a main beam light-guiding element
according to the invention,
[0034] FIG. 8 an illustration of the light intensity distribution
of the main beam light-guiding element from FIG. 7,
[0035] FIG. 9 an intensity profile curve of the light intensity
distribution from FIG. 8,
[0036] FIG. 10 a vertical section through a main beam light-guiding
element according to the invention, and
[0037] FIG. 11 a detail from FIG. 10.
[0038] FIG. 1 shows a perspective illustration of the basic
structure of a lighting device 1 according to the invention. The
lighting device 1 comprises a plurality of LED light sources 100,
not illustrated in greater detail in FIG. 1 (but see FIG. 7 for
further details), and an optical attachment 10 (=primary optics)
positioned in the light radiation direction, and a downstream
imaging optics 200 (illustrated as an individual lens 200). The
optical attachment 10 comprises light-guiding elements 11, 12, 13,
which are arranged in three rows and which extend on the radiation
side to a joint end plate 26. The end plate 26 is delimited on the
radiation side by a light exit face 23', wherein the light exit
faces 23 of the individual light-guiding elements (see FIG. 7) are
each part of the joint light exit face 23', wherein individual
light exit faces 23 border one another. The joint light exit face
23' is typically a curved face, which usually follows the Petzval
face of the imaging lens 200. For specific applications, deliberate
deviations in the curvature of the joint light exit face 23' can
also be inserted in order to utilise imaging errors in the edge
region for light homogenisation. Each light-guiding element 11, 12,
13 is assigned an LED light source 100 (see FIG. 7) in a manner
known per se. The lighting intensity can be individually controlled
for each light-guiding element 11, 12, 13, and therefore any
desired light distributions can be realised. In the case of the
optical attachment 10 shown in FIG. 1, the upper row is configured
as a forefield row consisting of a plurality of forefield
light-guiding elements 13. The middle row is configured as an
asymmetry row consisting of a plurality of asymmetry light-guiding
elements 12, and the lower row is configured as a main beam row
consisting of a plurality of main beam light-guiding elements 11.
The three rows in the activated state together form a main beam
distribution. The main beam light-guiding elements 11 are provided
on their lower light-guiding face 24 (see FIG. 7 in this respect)
with a rib structure 25, wherein the ribs 25 are oriented
transversely to an optical axis 16 of the lighting device 1. FIG. 3
shows a detailed view of the optical attachment 10 from FIG. 1 in
the light propagation direction.
[0039] The light-guiding elements 11, 12, 13 can be produced for
example from silicone, plastic, glass, or any other materials
suitable for guiding light. The light-guiding elements 11, 12, 13
are embodied as solid bodies and consist of a single continuous
optical medium, wherein light is guided within this medium. The
light-guiding elements 11, 12, 13 have a substantially square or
rectangular cross-section and widen in the light radiation
direction, where they ultimately extend on the radiation side to a
joint end plate 26, as described above, which is delimited on the
radiation side by a light exit plane 23' (see FIG. 3).
[0040] FIG. 2 shows an illustration of the total light distribution
(=pixel light distribution) as viewed through the imaging lens on a
measuring screen that can be obtained with the lighting device 1
from FIG. 1. Therein, fields arranged in three rows in a matrix
-like manner around a horizontal axis U and a vertical axis V can
be seen, wherein the upper row, which comprises a plurality of main
beam strips, serves to light the main beam region, the middle row
serves to light in the asymmetry region (formation of the
light-dark boundary), and the lower row serves to light the
forefield of a pixel light headlamp. On the whole, the light
distribution forms a main beam distribution. Adjacently arranged
fields contact one another or overlap one another, whereby the
light pattern appears substantially homogeneous to an observer.
[0041] FIG. 4 shows a side view of a main beam light-guiding
element 11' according to the prior art. The main beam light-guiding
element 11' is a solid body with a light input face 21, via which
the light radiated from the LED light source is coupled into the
light-guiding element 11'. The light is guided forwards along the
main beam light-guiding element 11' to a light exit face 23. FIG. 4
also shows exemplary beam paths starting from the light input face
21., wherein the beams 50 represent the direct light exit and the
beams 51, which are reflected on a lower light-guiding face 24,
represent the indirect light exit. The upper light-guiding phase 22
can also be seen, whereas the light-guiding faces laterally
delimiting the solid bodies are not provided with reference signs
for reasons of clarity. The light beams are totally reflected at
the light-guiding faces. As can be clearly seen from FIG. 4, the
lower light-guiding face 24 of a main beam light-guiding element
11' is formed in accordance with the prior art along its entire
length as a smooth reflection face (optimised for use for total
reflection).
[0042] FIG. 5 shows, by way of example, a light intensity
distribution 30 (light ray tracing simulation with a light
intensity sensor, wherein a grey-scale image, corresponding to the
light intensity, is obtained) of a main beam light-guiding element
11' from FIG. 4. In the lower region of the main beam segment, an
intensity maximum 31 can be defined; in the upper region of the
main beam segment, there is by contrast firstly an intensity drop
32, which leads, due to a counterincrease 33 in the intensity, to a
clearly visible inhomogeneity. FIG. 6 shows an intensity profile
curve of the light intensity distribution from FIG. 5, in which the
counterincrease 33 can be clearly seen. The reason for the
modularity lies in particular in the transition and defective
overlap between the directly radiated light 50 and the light 51
reflected at the lower light-guiding face 24.
[0043] FIG. 7 shows a side view of a main beam light-guiding
element 11 according to the invention. The main beam light-guiding
element 11 according to the invention differs from that from the
prior art (main beam light-guiding element 11', see FIG. 4) in that
rib-like structures 25 are formed on the lower light-guiding face
24 in the region in which the beams 52 are reflected. The rest of
the structure of the main beam light-guiding element 11 corresponds
to that from FIG. 4, and reference is made to the description
further above in this regard. FIG. 7 also shows exemplary beam
paths starting from the light infeed face 21, wherein the beams 50
represent the direct light exit and the beams 52, which are
reflected at the rib structure 25 of the light-guiding face 24,
represent the indirect light exit. The rib structure 25 scatters
and shapes the light 52 precisely in the region lying in the
transition between the directly radiated light 50 and the light 52
reflected at the rib structure 25 of the lower light-guiding face
24. The light distribution can be influenced by the rib structure
25, consequently resulting in an improvement of the light
homogeneity.
[0044] FIG. 8 shows, by way of example, a light intensity
distribution 30' (light ray tracing simulation with a light
intensity sensor, wherein a grey-scale image, corresponding to the
light intensity, is obtained) of a main beam light-guiding element
11 according to the invention from FIG. 7. In the lower region of
the main beam segment, the intensity maximum 31 can be defined; in
the upper region of the main beam segment, a continuous drop in the
intensity can generally be seen, and the light pattern is much more
homogeneous compared to the prior art. FIG. 9 shows an intensity
profile curve of the light intensity distribution from FIG. 8, from
which the continuous intensity drop and the improved homogeneity
(marked in FIG. 7 by the reference sign 34) in the transition
between the directly radiated light 50 and the light 52 reflected
at the rib structure 25 can be clearly seen. With the aid of the
rib structure, the run-out upwardly (see FIG. 2) can be better
designed or optimised.
[0045] FIG. 10 shows a vertical section through a main beam
light-guiding element 11 according to the invention. As can be seen
therein, the ribs 25 extend transversely to the optical axis (or
light propagation direction) and along a (virtual) carrier curve TK
on the lower light-guiding phase 24. In the shown example, a total
of 9 ribs are formed starting from the light exit face 23. The ribs
25 for example have a width of 0.3 mm and a height of 0.015 to 0.03
mm.
[0046] FIG. 11 shows a detail from FIG. 10 (shown in FIG. 10 by a
dashed circle). An optimised embodiment can be obtained as follows:
The carrier curve TK is, here, the delimitation of a light-guiding
element. Points P (Pi, Pi+1, Pi+2) are plotted on this curved
(virtual) curve TK, which points have a constant distance S from
one another. This distance (or wavelength) is for example S=0.30 mm
for a specific main beam light-guiding element. Adjacent points Pi
and Pi+1 define a path, at the midpoint Hi of which a normal is
established. An apex point Si is established above the point at a
distance=amplitude of hi. The three points Pi, Si, Pi+1 are the
grid points of a spline curve. The magnitude of the amplitude is
iteratively varied, and a light-based simulation is performed in a
manner known per se with the corresponding geometry. By comparison
of the obtained light patterns (or of the gradient profile), the
best amplitude is determined. This procedure must be repeated for
each rib, since the distance from the light source (LED light
source 100) defines the angle of incidence on the carrier curve and
therefore the position of the inhomogeneity. The delimiting face of
the rib itself is an extraction face of the determined spline
curve, wherein the extraction direction is normal to the vertical
middle plane of the light-guiding element, and wherein each rib has
its own amplitude.
[0047] The shown examples are just some of many, and are not to be
interpreted as limiting.
* * * * *